"Shark Tank" investor Robert Herjavec's cybersecurity firm, the Herjavec Group, brought in $140 million in revenue last year. But he tells Business Insider he was not a born entrepreneur.

"Mark Cuban and I always argue about this," Herjavec says. "He's always, 'Oh, when I was 12 I knew I was going to start my own business.'"..."When I was 12," he says, "I didn't know anything. I just wanted to go outside and play."

Herjavec writes in his 2010 book, "Driven," that after he graduated college he lacked direction. He decided to get two jobs as a waiter, one at an upscale restaurant and one at a casual one, to support himself until inspiration struck. The jobs impacted him more than he ever expected.

He writes that "over the course of 25 years since then, I have often reflected on things I learned about people, about business, and about myself while waiting on tables. Herjavec lists six business lessons he learned from having to deal with people every night as a waiter.

You can't choose all of your customers.

Diners are assigned servers according to what part of the restaurant needs to be filled, not according to how skilled the server is. That means that each server has a variety of customers on any given day.

Herjavec had to learn that some people will be more agreeable and generous than others, but that all will expect their needs to be met.

"Selling to people who share your interests is easy," he writes. "Selling to people with whom you have nothing in common isn't, but it's necessary."

The customer isn't always right.

Herjavec says he'd often deal with customers whose anger or frustration with their order would be directed at him. And while he knew it wasn't his fault, he learned that it was necessary to always have a customer leave happy, through the help of a complimentary drink or dessert.

As in business, a "sincere show of concern on my part" can win over unhappy customers, whether their unhappiness is justified or not.

Empower employees to handle problems on their own.

Most customers, Herjavec says, want to have their server address their problem rather than have to go to a manager. "They want to focus on someone who understands their concern and can solve it on the spot."In a business setting, this means having the CEO empower employees to handle crises without always seeking the help of a superior.

Take responsibility for both successes and failures.

In a restaurant, a server is often rewarded or penalized for a great meal, regardless of the fact that they has nothing to do with the food. Similarly, business managers need to take responsibility for all of their team members' work, regardless of how involved they were.

Be polite to rude customers.

Reacting to a rude customer never yielded a good result, Herjavec says."Managing to be pleasant and civil in the presence of rudeness, on the other hand, can provide surprising rewards," he writes.

Never appear overwhelmed.

"Diners and customers alike value coolness under pressure," Herjavec writes. He says that if he had to take a breath or throw a tantrum, it would always be in the kitchen, not in the dining area. The same principle applies in an office setting or public appearances representing your company